Seems to me that the "official" walkthrough missed a very important strategy that I have found the easiest way to win, and at the same time research up to and build strong enough forces.

Usually the first real headache is the Gorilla/Reaper/Wasp attack from the West. After a zillion tries, I still don't know if turrets are worth it. I found Triple Plasma Knights in FP just blow away the Gorillas. You do kinda want to build an antiaircraft gun just north of the original mine.

Take advantage of the ready made researcher labs and use 1 tech for the civilian lab. Get the Scavenger deal going, and get an aircraft factory. Wjat blows is you are limited to the plasma wasps, so I just make APCs, about three.

All the while you should crank out Triple Plasma knights with your limited BMU's. Recycle the Mek. I used to build Leviathans but I don't anymore. Knights in FP do the trick.

In the walkthrough, the idea is to push up the main "road" and infiltrate and reclaim the buildings, This is fun, but the enemy is very busy attacking your bases - usually with turret reapers. You can get caught out here.
Thats why I get APC's going, and do an "end run" around the whole thing, capturing the buildings in the extreme NE of the map. I bring knights builders and at least one transporter. You can capture the air unit factory and smelter there and just press forward, capturing or destroying as you need to and then its attrition once the smelters are captured.
Just WATCH OUT for the ion cannon! If you can capture it, well, you can kick some major metal butt!

Build lots of factories so I won't run dry of infantry, and even if I do I can produce more machines fast.

I don't really care about the Wasps, they can be easily killed if you have a few Knights and even more Reapers. Eventually if you do bizarre moves with your machine in 1st person mode, you can get rid of them fast (it's a bit harder, though, since rocket wasps are accurate!).

Spam Assassin Warlords/Knight Templars once I have the opportunity, they deal lots of damage and, well, they're awesome! Not to mention circling around Gorillas is especially efficient with these units.

I never really liked to use Scavengers (it's very efficient, though, just not my style), so I just search for minerals as fast as I can and build extractor mines everywhere.

Try to find the Satellite Uplink and protect it, being able to see the whole map is cool and helpful. It also doesn't trigger event flags, so I can prepare myself for the Ion Cannon flag.

Destroy those annoying factories built inside the city once I spot them.

I love to trigger event flags before they're supposed to be triggered. That way, I can make Gorillas come a bit faster and then they'll DIE because my infantry will eradicate them (if I use the awesome 1st person mode). After that, the enemy's army will be "slightly" less powerful. Of course, discounting the Ion Cannon flag, which is probably the only headache for me.

I don't really build turrets, they're not very useful in Machines (unless your enemy's infantry doesn't use 1st person mode). That's a shame... but the Leviathan turrets are awesome. Never really constructed turrets, anyway, only to win a match against an enemy in Oasis.

The only mission that was real pain for me was the "Behind the enemy lines" mission. It was fun to figure out how to get the Commander from point A to point B, though.